Keeping in mind the purpose of this technology is not an alternative to a solar panel or wind power but supplementary energy source to capture waste heat.

Imagine being able to run this as tubing over nuclear \ coal plants water cooling pipes where you can get heat upto 300 C +. This would exponentially boost the efficiency of current generation plants that have massive heat byproducts.

Is it possible to have a panel that can run in "normal" mode at normal efficiencies during the day and then switch to this new mode at night?

That's what I was wondering; some kind of combined photovoltaic/thermoradiative panel? And...what about tacking on a battery of some kind to the whole shebang to retain energy in case of shortfalls day-to-day?

How is this different than a thermal electric generator? The tech has been around since the 19th century and used for nuclear powered space craft and remote points since the 50s. radioisotope thermoelectric generators...

Well good ideas keep coming around. The better idea might be to store hot water heated by solar panels then pump the hot water into a TEG at night to generate power. Might be better than batteries, with a lower cost storage medium.

Does this mean the researchers have/had no wafers? This is just theorycrafting at the moment, with nothing produced even for a test?Mercury Cadmium Tellurium compounds sound very expensive.Sounds really great, especially if you can use the waste heat from high heat applications to generate power at night.

Regarding using this on a nuclear powered ship - probably easier to drop a tube down into cold water and use that heat gradient instead. Not that either is likely to be worth the bother since it might increase the efficiency of the nuclear power generator by .01% or some other tiny amount.

In a non power generating application, it would be interesting to see if that IR window could be employed to dump very large amounts of heat off the planet. Putting a big radiator on a part of the planet now, even on a cloudless night, will mostly just move the heat up into the atmosphere, whereas a high power IR laser in the right wavelength band could dump it all the way out into space and actively cool the planet. Before anybody asks, no, I have not thought through the thermodynamics of this. It might well be that it is not even theoretically possible to move that much power into an IR laser without emitting even more power locally to the environment while doing so.

So is the main benefit here that your cold side temperature is effectively very low (outer space, single digit K?), giving you high thermodynamic efficiency by maximizing delta T?

Still, it seems that you need a large radiating surface, so unless this can be implemented as part of traditional PV panels (as others have suggested), it sounds like you'd better off with regular PV + batteries.

Agreed that this sounds more like a thermal electric generator that rejects heat into space, rather than "reverse solar panel".

How is this different than a thermal electric generator? The tech has been around since the 19th century and used for nuclear powered space craft and remote points since the 50s. radioisotope thermoelectric generators...

Well good ideas keep coming around. The better idea might be to store hot water heated by solar panels then pump the hot water into a TEG at night to generate power. Might be better than batteries, with a lower cost storage medium.

The trick with this is that by radiating into space the cold side of your TEG is now 2.7 Kelvin and has effectively limitless heat capacity. The bad news is that the flux is very low.

If I recall (this may be outdated knowledge now and may be biased as I was researching it from an e-waste hazard standpoint), most of the higher yield cells tended to be rather toxic with the exception of indium (for "cloudy" solar), which was what I thought this article was initially going to be about.

Interesting... in the southern US, one of the major uses of electricity is in cooling.

These devices produce electricity by cooling. So the inefficiencies may not be as bad as they appear, if by generating the electricity, you're already doing a portion of the work the electricity was being generated to do. For a passive system, this does have promise; especially if they can make it affordable to manufacture and adaptable for rooftops. Bonus if they can make the panels transparent and build them into windows; because unlike PVCs, these things don't need to track the sun; they just need to radiate in a fixed band.

So, using the typical sky 10 W/m^2 from the paper and the 162,494 TWh 2017 energy production from Wikipedia, it would take ~1.8 million km^2 of this stuff to power the Earth. That's approximately than the surface area of Texas, Montana, and California combined.

So, using the typical sky 10 W/m^2 from the paper and the 162,494 TWh 2017 energy production from Wikipedia, it would take ~1.8 million km^2 of this stuff to power the Earth. That's approximately than the surface area of Texas, Montana, and California combined.

Well you're not powering the Earth. You're only powering the greatly reduced power consumption that occurs overnight. The idea is to offset the storage requirement typically associated with solar.

Read about this somewhere else yesterday evening. Didn't understand how it worked. This article is much better for a layman science geek, who's bad at higher math.

The basic science is surprisingly easy to demonstrate. Get ahold of a common infrared thermometer, take it outside. Confirm that it's working by pointing at anything solid nearby. It should read the same as a regular thermometer for objects in the shade. Then point it at a patch of clear sky. It'll show a temperature that is off-the-scale below zero. Clouds read somewhat below freezing on the thermometer I use in my kitchen.

So, using the typical sky 10 W/m^2 from the paper and the 162,494 TWh 2017 energy production from Wikipedia, it would take ~1.8 million km^2 of this stuff to power the Earth. That's approximately than the surface area of Texas, Montana, and California combined.

How is this different than a thermal electric generator? The tech has been around since the 19th century and used for nuclear powered space craft and remote points since the 50s. radioisotope thermoelectric generators...

Well good ideas keep coming around. The better idea might be to store hot water heated by solar panels then pump the hot water into a TEG at night to generate power. Might be better than batteries, with a lower cost storage medium.

You can do work any time you find a way to harness a flow of energy - and energy moves all the time. Nothing like deep space as the cold source of a Carnot cycle.

Considering the energy radiation to space is important in several circumstances. Most people would encounter it with trying to keep a swimming pool warm - a little insulation at night does a lot to help. This is also how the ancients made ice in the desert even when ambient temperatures don't drop below freezing.

Regarding using this on a nuclear powered ship - probably easier to drop a tube down into cold water and use that heat gradient instead. Not that either is likely to be worth the bother since it might increase the efficiency of the nuclear power generator by .01% or some other tiny amount.

In a non power generating application, it would be interesting to see if that IR window could be employed to dump very large amounts of heat off the planet. Putting a big radiator on a part of the planet now, even on a cloudless night, will mostly just move the heat up into the atmosphere, whereas a high power IR laser in the right wavelength band could dump it all the way out into space and actively cool the planet. Before anybody asks, no, I have not thought through the thermodynamics of this. It might well be that it is not even theoretically possible to move that much power into an IR laser without emitting even more power locally to the environment while doing so.

A nuclear powered aircraft carrier could dump it's waste heat into these thermoradiative panels to harvest electricity, where there is no means to 'tap into the Earth'.

Likewise in the desert where the night time temperature is over 100F, and you're running AC, meaning your compressor can get to be 200F or 300F easy depending on how large it is and how much it runs.

So at night time you can harvest this heat to get a little bit of electricity and cool the condenser.

Aircraft carriers float in an effectively infinite heat sink. And they pack 1100 MWt into two 20 m2 reactors. This isn’t going to move the needle at all for them.

Actually, given the temperature difference you would tune the device to radiate into the water instead of the sky, if you cared.

My point isn't that the sky is an effective heatsink, my point is that the temperature difference between the sky and the generators would guarantee the ability to harvest waste heat for additional electricity.

All of those places will be running AC at night, and the combination of buildings retaining heat + AC generating heat means that there will be plenty of heat to collect; the article mentions running at 80°F

If you have waste heat at 170C, just use it to drive a conventional steam engine. You would easily get around 30% efficiency.

It gets down to price to implement and maintain. Fixed panels are usually easy to maintain. Turbine systems... less so. Recovery of waste heat is a big topic, but even when it's "economical" it's sometimes too complicated or too far removed from a core business to want to jump into. That's why you don't see an algae plant at every refinery, or a distilled water plant at every nuclear reactor.